Method and systems for isolation and/or separation of target products from animal produced waste streams

ABSTRACT

The present invention relates to separation methods and systems for converting high concentrations of animal wastes into useful products, wherein the separation of the desired useful products is conducted with a cross-flow filtration system having the ability to the separate desired useful energy and/or products from both viscous and non-viscous medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/735,276 filed on Jun. 10, 2015, now U.S. Pat. No. 10,005,697, whichis a Continuation-in-Part application claiming priority to U.S. patentapplication Ser. No. 13/985,367 filed on Oct. 30, 2013, now U.S. Pat.No. 9,163,265, which in turn is an application filed under theprovisions of 35 U.S.C. § 371 and claiming priority to InternationalPatent Application No. PCT/US2012/025874 filed on Feb. 21, 2012, whichin turn claimed priority to U.S. Provisional Patent Application Ser. No.61/445,010 filed on Feb. 21, 2011, the contents of which are allincorporated by reference herein for all purposes.

BACKGROUND OF THE INVENTION Field of Invention

The present invention relates to generally to the problems associatedwith waste in animal confinements, and more specifically, to separationmethods and systems for converting high concentrations of animal wastesinto useful products, wherein the separation of the desired usefulproducts is conducted with a cross-flow filtration system having theability to the separate desired products from both viscous andnon-viscous medium.

Related Art in Technical Field

The cleanup and handling of dairy cattle, beef cattle, swine and poultrymanure has become a critical issue in the management and disposal ofanimal waste. Animals have been raised for centuries for food andpreviously such animals grazed in fields or pens. Current methods ofraising livestock include housing in high concentration within aconfined space. Numerous drawbacks of such confinement include emotionalstress on the animals but also high concentrations of waste that must beremoved from the confined space.

The manure produced must be removed regularly to ensure adequatesanitation and to prevent disease. One manure removal method is to floodthe housing area with water in order to wash away the manure. Theresulting effluent, that being a liquid/solid manure slurry, istypically directed through pipes or channels to a manmade slurry pond orlagoon, where the solids and particulates settle to the bottom and theanimal waste decomposes. After some decomposing, the waste can beapplied as a fertilizer. Additionally the liquid/solid manure can bedirected to a biodigester to capture some of the gaseous components ofthe manure and use the gases for energy, thereby reducing air qualityissues of manure accumulation and storage. However, the remainingliquids and solid from biodigestor processing must still be addressed tominimize loss or nutrient contamination of lagoons, fields, drinkingwater, wells, or fresh water streams or lakes.

Notably, prolonged mixing of solid and liquid wastes in a waste manurelagoon can result in the transfer of a significant amount of nutrientsfrom the solid material to the surrounding liquid, so that the solidsbecome depleted of nutrients that may be desirable in a manurefertilizer. However, the liquids become loaded with nitrogen,phosphorous and salts to such an extent that they must be either limitedin their irrigation use, or mixed with fresh water to lower theproportion of these substances. In other words, the useful qualities ofboth the solid and liquid portions of the slurry mixture are degradedover time in a slurry pond or lagoon.

Further, the environmental impact can be substantial when applying thewaste to fields. Such environmental issues may include ground leachingfrom the lagoon causing contamination of ground water and/or streams andsand soil contamination. Additionally, the high volume of solid wastemanure, coupled with it use as fertilizer in local fields, results inincreased levels of phosphorus, potassium and heavy metals in the soils.This may allow such minerals to also leach into drainage waters andrun-off streams. The high volume of liquid waste manure, coupled with ituse as fertilizer in local fields, results in increased levels ofnitrogen rich ammonium and ammonia in the soils. This may allow suchminerals to also leach into drainage waters and run-off streams.

There has been increasing publicity and stricter environmentrequirements and enforcement because of the continuing concern overmaintaining water quality in watershed areas due to the release ofmanure as normal operational discharges from dairy cattle, beef cattle,swine, poultry and other confined animal feeding operations. Currenttechnologies for separating solids and nutrient components of suchanimal waste have limitations, are costly to operate, and result in theuse of large quantities of fuel and labor in order to provide solid andwater-based effluents that can either be recycled or are environmentallyacceptable to spread on farmlands.

Thus, what is needed is an improved process and separation system fortreating animal waste that is low in capital equipment cost, low inwaste transportation cost, simple to operate, and that provides solidand liquid effluents containing beneficial and useful products.

SUMMARY OF THE INVENTION

The present invention relates to separation systems and methods toprocess a manure source containing urine and fecal matter from dairycattle, beef cattle, swine, sheep, goats, poultry, horses, rabbits andother confined animals to provide at least a liquid fertilizer and aconcentrated viscous fertilizer that can be dried to a solid form. Othertarget products may be separated from either the liquid or concentratedviscous fertilizer including, but not limited to, nitrogen, potassium,potable water, filtrate with reduction of residuals for spraying onfields, and/or phosphorus.

In one aspect, the present invention provides a process for treatingmanure in order to produce a liquid fertilizer and a concentratedviscous fertilizer, the process comprising:

-   -   providing a manure medium;    -   separating the manure into the liquid fertilizer and the        concentrated viscous fertilizer by passing through a cross-flow        filtration cassette comprising:    -   an array of sheet members of generally rectangular and generally        planar shape with main top and bottom surfaces, wherein the        sheet members include in sequence in said array a first        retentate sheet, a first filter sheet, a permeate sheet, a        second filter sheet, and a second retentate sheet, wherein each        of the sheet members in said array has at least one inlet basin        opening at one end thereof, and at least one outlet basin        opening at an opposite end thereof, with permeate passage        openings at longitudinal side margin portions of the sheet        members, wherein each of the first and second retentate sheets        having a multiplicity of channel openings therein, extending        longitudinally between the inlet and outlet basin openings of        the sheets in the array, and being bonded to an adjacent filter        sheet about peripheral end and side portions thereof, with their        basin openings and permeate passage openings in register with        one another and the permeate passage openings of each of the        retentate sheets being circumscribingly bonded to the adjacent        filter sheet, and with a central portion of each of the        retentate sheets and adjacent filter sheets being unbonded to        permit permeate contacting the retentate sheet to flow through        the filter sheet to the permeate sheet; and    -   wherein the liquid fertilizer is in the permeate stream and the        concentrated viscous fertilizer remains in the retentate stream.

Livestock manure besides containing a mixture of feces and urine mayalso include wasted feed, bedding and water (including: spilled water,flush water, wash water, and precipitation). Manure characteristics aregenerally affected by diet, species and the growth stage of the animals,and the manure collection method used, including the amount of wateradded to dilute the waste. Typically, animal waste manure is about 80%to about 95% liquid by weight due to urine, sloppy drinking, animalwashing and flush water. As such, the manure medium may be pretreatedwith mechanical system to remove any unwanted material, larger solidsand excess liquids from the manure medium before introduction into thecross-flow filtration cassette, wherein the pretreating includes systemssuch as screw press, centrifuge, vibrating screen, mesh screening, beltfilter, hydrocylcone and other systems that may further reduce particlesize, and/or remove unwanted large material to ensure easy flow throughthe cross-flow filtration cassette of the present invention.

Further, the manure may be pretreated in an anaerobic digester, whichincludes holding manure in an air-tight tank that is heated to about 100degrees—just like a cow's stomach. Bacteria in the manure thrive inthese conditions and they consume solids in the manure while releasingmethane gas. Naturally occurring bacteria will degrade the volatilesolids (VS), releasing a combination of carbon dioxide (CO₂) and methane(CH₄) that may be burned/combusted for energy production. Digestion doesnot reduce the nutrients in the manure, although it may alter the formof the nitrogen (more ammonia) and phosphorus (more orthophosphate).

Optionally the liquid fertilizer which contains at least phosphorus andnitrogenous compounds can be further treated to remove additional“valuable” nutrients such as soluble phosphorus (SP). The addition ofmagnesium chloride (MgCl₂) may be used to force the precipitation ofstruvite (MgNH₄PO₄.6H₂O). Notably, adjusting the pH of the treatedliquid concentrate to a pH of about 9.0-10 with sodium hydroxide (NaOH)can increase SP reduction and formation of struvite.

Further, ferric chloride (FeCl₃), ferric sulfate (FeSO₄), calciumhydroxide (lime), aluminum sulfate (alum) and aluminum chloride AlCl₃)can be used for phosphorus binding and the formation of commonphosphorus salts. The addition of these binding agents forms a solidsalt that can be collected and removed by cross-flow filtrationcassettes of the present invention.

Still further, the manure medium may be treated with chemicals to helpseparate solids from liquids. Flocculation is a process that convertscoagulated particles into large, rapidly settling masses, also calledflocs. The most common chemicals used to coagulate and flocculate solidsin animal manure and wastewater are organic polymers such aspolyacrylamide (PAM), and metal salts such as ferric chloride (FeCl₃),alum (Al₂(SO₄)₃) and lime (Ca(OH)₂). Such flocs can be further removedby screening methods or centrifuging.

In another aspect, the present invention provides for a separationmethod of at least one target product from a manure medium in a viscousor non-viscous liquid form, the method comprising the steps of:

-   -   providing a manure medium in a vessel wherein the manure medium        comprises the at least one target molecule, wherein the at least        one target product is selected from the group consisting of        nitrogen, potable water, filtrate with reduction of residuals,        and phosphorus;    -   providing at least one cross-flow filtration cassette        comprising:    -   an array of sheet members of generally rectangular and generally        planar shape with main top and bottom surfaces, wherein the        sheet members include in sequence in said array a first        retentate sheet, a first filter sheet, a permeate sheet, a        second filter sheet, and a second retentate sheet, wherein the        liquid medium to be filtered flows across the filter sheets,        solids or high-molecular-weight species of diameter larger than        the filter sheet's pore size, are retained in the retentate        flow, and at least a portion of the liquid medium with any        permeate species diffuse through the filter sheets and enter the        permeate sheet and permeate flow; wherein each of the sheet        members in said array has at least one inlet basin opening at        one end thereof, and at least one outlet basin opening at an        opposite end thereof, with permeate passage openings at        longitudinal side margin portions of the sheet members, wherein        each of the first and second retentate sheets having a        multiplicity of channel openings therein, extending        longitudinally between the inlet and outlet basin openings of        the sheets in the array, and being bonded to an adjacent filter        sheet about peripheral end and side portions thereof, with their        basin openings and permeate passage openings in register with        one another and the permeate passage openings of each of the        retentate sheets being circumscribingly bonded to the adjacent        filter sheet, and with a central portion of each of the        retentate sheets and adjacent filter sheets being unbonded to        permit permeate contacting the retentate sheet to flow through        the filter sheet to the permeate sheet;    -   effectuating a sufficient flow of the manure medium comprising        the target product from the vessel through at least one        cross-flow filtration cassette; and    -   sequentially capturing one or more filtration fractions        generated by the cross-flow filtration modules, wherein the        target product is physically separated by said one or more        cross-flow filtration and wherein said physical separation of        target product is based on their different molecular weights,        size and/or operating conditions.

In a still further aspect, the present invention provides for a processfor treating manure in order to produce fertilizer products and potableor non-potable water, the process comprising:

providing a manure slurry;

-   -   passing the manure slurry through a first cross-flow filtration        cassette comprising:    -   an array of sheet members of generally rectangular and generally        planar shape with main top and bottom surfaces, wherein the        sheet members include in sequence in said array a first        retentate sheet, a first filter sheet, a permeate sheet, a        second filter sheet, and a second retentate sheet, wherein each        of the sheet members in said array has at least one inlet basin        opening at one end thereof, and at least one outlet basin        opening at an opposite end thereof, with permeate passage        openings at longitudinal side margin portions of the sheet        members, wherein each of the first and second retentate sheets        having a multiplicity of channel openings therein, extending        longitudinally between the inlet and outlet basin openings of        the sheets in the array, and being bonded to an adjacent filter        sheet about peripheral end and side portions thereof, with their        basin openings and permeate passage openings in register with        one another and the permeate passage openings of each of the        retentate sheets being circumscribingly bonded to the adjacent        filter sheet, and with a central portion of each of the        retentate sheets and adjacent filter sheets being unbonded to        permit permeate contacting the retentate sheet to flow through        the filter sheet to the permeate sheet; and    -   wherein a viscous stream phase remains in the retentate stream        and a liquid stream phase is the permeate stream;    -   passing the permeate stream through a second cross-flow        filtration cassette of the present invention wherein a liquid        fertilizer concentrate is retained in the retentate stream and a        permeate filtrate constitutes recyclable water.

Alternately, the permeate stream can be passed through a conventionalnanofiltration or reverse osmosis spiral to create recyclable orreusable water.

The liquid stream phase may be utilized as the liquid fertilizer and theviscous stream phase may be dehydrated to minimize water content andprovides for a solid fertilizer. Preferably, the viscous stream is driedto a consistency of less than 15% moisture and more preferably to about10% or less moisture to avoid bioactivity and degradation. In apreferred embodiment the retentate comprising the viscous material iscast or extruded in a thin film onto a conveyor belt which is thenintroduced into a chamber that comprises a system to provide a thinuniform layer of the viscous material. Such systems may include aroller, extrusion die, knife box or doctor blade to produce a thinconsistent film layer of the viscous material. Such thin consistentlayers provide for efficient and faster drying, reduction of energycosts and consistency in the end product, which is flake or powder thatis easily removed from the conveyor belt system and also suitable foruse as a dry fertilizer. Optionally a heating system is included toincrease the speed of the drying process.

In yet another aspect, the present invention provides for production ofpotable and non-potable water, the method comprising:

-   -   moving a manure slurry through a first cross-flow filtration        unit according to the present invention wherein such manure        slurry is separated and waste water containing residues is        separated into a permeate stream and the remaining viscous        retentate stream is collected for further use;    -   moving the permeate stream through a second cross-flow        filtration unit according to the present invention wherein the        waste water is separated providing permeate stream depleted of        the residues and a residue containing retentate; and    -   moving the permeate stream depleted of the residues through a        third cross-flow filtration unit according to the present        invention, wherein the permeate stream is purified and provides        for potable water and/or non-potable that is acceptable for        animal drinking water.

Other aspects and advantages of the invention will be more fullyapparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the components of a cross-flow filtration cassette used inthe separation of renewable fuels

FIG. 2 shows the flow pattern of the retentate through a multiplicity ofsheets adapted to end plates with retentate inlet and outlet andpermeate inlet and outlet.

FIG. 3 shows a system for separating manure slurry.

FIG. 4 illustrates the consistency of the source manure introduced intothe vessel 14 (left side of the photo) and the increased viscosity ofthe concentrate (right side of the photo) after processing in the systemof FIG. 3.

FIG. 5 shows the difference in amounts of specific elements of both amanure digestate and screen raw manure after processing in the system ofFIG. 3.

FIG. 6 shows the filtration difference when using two different filterscreens in the cross-flow filtration cassette of the present invention.

FIG. 7 shows that NH₃/NH₄ passes freely through the cross-flowfiltration cassette of the present invention to provide a rich Nfraction in the permeate.

FIG. 8 shows a perspective view of an extruder and drying system.

DETAILED DESCRIPTION OF THE INVENTION

While not to be construed as limiting, the terms used herein have thefollowing definitions unless indicated otherwise.

The term “manure” refers to any material that includes animal waste andmay include but is not limited to water, feed, urine, fecal matter,straw, hay, bedding material, peat moss, and composts.

The term “cross-flow filtration cassette” refers to a type of filtermodule or filter cassette that comprises a porous filter element acrossa surface of which the liquid medium to be filtered is flowed in atangential flow fashion, for permeation through the filter element ofselected component(s) of the liquid medium. In a cross-flow filter, theshear force exerted on the filter element (separation membrane surface)by the flow of the liquid medium serves to oppose accumulation of solidson the surface of the filter element. Cross-flow filters includemicrofiltration, ultrafiltration, and nanofiltration systems. In apreferred embodiment, the cross-flow filter comprises a multiplicity offilter sheets (filtration membranes) in an operative stackedarrangement, e.g., wherein filter sheets alternate with permeate andretentate sheets, and as a liquid to be filtered flows across the filtersheets, impermeate species, e.g. solids or high-molecular-weight speciesof diameter larger than the filter sheet's pore size, are retained andenter the retentate flow, and the liquid along with any permeate speciesdiffuse through the filter sheet and enter the permeate flow. In thepractice of the present invention, cross-flow filtration is a preferredseparation method. Cross-flow filter modules and cross-flow filtercassettes useful for such filtration are commercially available fromSmartflow Technologies, Inc. (Apex, N.C.). Suitable cross-flow filtermodules and cassettes of such types are variously described in thefollowing U.S. Pat. Nos. 4,867,876; 4,882,050; 5,034,124; 5,034,124;5,049,268; 5,232,589; 5,342,517; 5,593,580; and 5,868,930; thedisclosures of all of which are hereby incorporated herein by referencein their respective entireties.

In one particular aspect, the present invention relates to a cross-flowfiltration cassette, as shown in FIG. 1, comprising a multilaminatearray of sheet members of generally rectangular and generally planarshape with main top and bottom surfaces, wherein the sheet membersinclude in sequence in said array a first retentate sheet, a firstfilter sheet, a permeate sheet, a second filter sheet, and a secondretentate sheet, wherein each of the permeate and filter sheet membersin said array has at least one inlet basin opening 10 at one endthereof, and at least one outlet basin opening 12 at an opposite endthereof, with permeate passage openings 13 at longitudinal side marginportions of the sheet members; each of the first and second retentatesheets having at least one channel opening 8 therein, extendinglongitudinally between the inlet 10 and outlet basin 12 openings of thepermeate and filter sheets in the array, and being compression bonded toan adjacent filter sheet about peripheral end and side portions thereof,with their basin openings and permeate passage openings in register withone another and the permeate passage openings of each of the retentatesheets being circumscribingly compression bonded to the adjacent filtersheet, and with a central portion of each of the retentate sheets andadjacent filter sheets being unbonded to permit permeate contacting theretentate sheet to flow through the filter sheet to the permeate sheet;and each of the filter sheets being secured at its peripheral portionson a face thereof opposite the retentate sheet, to the permeate sheet.

The term “sheet” will denote the generally planar members of thecassette, the cassette thus comprising an assembly of permeate sheets,filter sheets, and retentate sheets, coupled to one another in suchmanner as to permit flow of the fluid to be separated through the flowchannel(s) of the device, for mass transfer involving passage of thepermeate through the filter sheets, and retention of the retentate onthe side of the filter sheet opposite the side from which the permeateemerges.

The term “compressible” in reference to the retentate sheet or otherstructural feature or sheet member of the present invention means thatsuch component or member is compressively deformable by application ofload or pressure thereon.

The above-described filtration cassette of the invention comprises a“base sequence” of elements, defined as a sequence of sheet elementsconstituting a compressible retentate sheet (hereafter designated by thesymbol “CR”), a filter sheet (hereafter designated by the symbol “F”), aforaminous permeate sheet (hereafter designated by the symbol “P”), asecond filter sheet (“F”), and a second compressible retentate sheet(“CR”), thereby providing a sequence of sheet elements, CR/F/P/F/CR.

The base sequence of sheet elements may be utilized in construction offilters comprising a plurality of filtration cassettes, wherein thecompressible retentate sheet is utilized to seal the top and bottomelements of a plurality of filtration cassettes of a sequence,comprising compressible retentate sheet “CR”, filter sheet “F”,foraminous permeate sheet P, filter sheet “F”, non-compressibleretentate sheet “R”, filter sheet “F”, foraminous permeate sheet P,filter sheet “F”, and compressible retentate sheet “CR”. An illustrativestacked cassette filter according to the invention may for examplefeature the sheet sequence CR/F/P/F/R/F/P/F/R/F/P/F/CR, comprising afirst compressible retentate sheet, two base sequences of sheets FPFRFPFin a repetitive sequence, and a second compressible retentate sheet. Inall repetitive sequences, other than a single cassette base sequence,the following relationship is observed: where X is the number of filtersheets F, the quantity 0.5 X-1 is the number of non-compressibleretentate sheets R, and the quantity 0.5 X is the number of foraminouspermeate sheets P, with two compressible retentate sheets being utilizedto seal the top and bottom extremities of the intervening sequence.

Thus, it is possible to utilize a large number of base sequencecassettes in a repetitive sequence, to provide a stacked cassette filterof the desired mass transfer area. Many configurations are possible. Itis feasible in some instances, e.g., for mass transfer studies andsystem quantitation, to utilize a single cassette comprising the basesequence CR/F/P/F/CR wherein the outermost retentate sheets in thesequence are compression-sealed at their outer faces to an end plateaccommodating removal of permeate from the permeate passage openings ofthe constituent sheet members in the cassette.

The sheets of filter material used in the cassette article of thepresent invention may be of any suitable porosity rating. As usedherein, the porosity rating of a sheet of filter material is thesmallest particle size which cannot pass through the pores of the filtermaterial. Typical porosity ratings are expressed in molecular weight(MW) and micrometer units, e.g., a 2 micron filter media sheet being amaterial which will pass particles smaller than 2 microns in diameterthrough the pores of the material, while particles larger than 2 micronswill not be passed through the filter material, and as a furtherexample, a 10,000 MW filter media sheet being a material which will passparticles smaller than 10,000 MW in diameter through the pores of thematerial, while particles larger than 10,000 MW will not be passedthrough the filter material.

Filters can be divided into categories based on the nominal molecularweight limits (NMWL) is an indication that most dissolved macromoleculeswith molecular weights higher than the NMWL and some with molecularweights lower than the NMWL will be retained by the membrane. Acomponent's shape, its ability to deform, and its interaction with othercomponents in the solution all affect its retention. Depending on themolecules to be retained, membrane NMWLs in the range of 1 kD to 500 kDmay be used in the present invention. For use in the present invention,the membranes are preferably in the range of 5 kD to 300 kD and morepreferably in the range of 10 kD to 100 kD.

In one preferred embodiment of the cassette article of the presentinvention, a retentate sheet is provided with a plurality oftransversely spaced-apart, longitudinally extending ribs or partitions,extending upwardly from (the central portion of) each of the main topand bottom faces of the retentate sheet, such ribs or partitions beingof substantially the same height and substantially parallel to oneanother to define a series of channels between the partitions, extendinglongitudinally between the respective basin openings of the retentatesheet, on both faces thereof. The adjacent filter sheets may be furtherbonded to the outer extremities of the ribs or partitions, and the ribsor partitions may be formed of any suitable material, e.g., a flexibleresilient adhesive bonding medium, such as a urethanes, epoxy orsilicone adhesive sealant medium, e.g., applied in a “bead” in thelongitudinal direction of the retentate sheet on both main top andbottom faces thereof.

The term “bonded” in reference to adjacent sheets in the multilaminatecassette means that the adjacent sheets are secured to one another insuch manner as to prevent flow of the material being processed, e.g.,the feed material to be separated, as well as component materialstherefrom (filtrate or permeate, as well as retentate), from flowingthrough such secured areas or between the adjacent sheets at suchsecured areas. Preferably, the bonding is carried out by compressivebonding or with a suitable adhesive or sealant medium, e.g., a urethane,epoxy, cyanoacrylate, or silicone adhesive material, which fills theinterstices of the foraminous sheet in the bonded pair of sheets, andadhesively joins one of the adjacent sheets to the other in the bondedareas.

The term “compressive bonding” and “compressively bonded” refer tobonding and bonding operations in which the structure being bonded issubjected to a compressive load or force, for sufficient time and undersufficient period to effect the bonding securement of the structure.Compressive bonding of laminae in the practice of the invention ishighly desirable, in order to assure the leak-tightness and structuralintegrity of the resulting multilaminate assembly of the cassette.

The invention may for example be carried out with bonding of sheets inthe multilaminate array to one another with cyanoacrylate or other“fast” adhesives, or alternatively the adhesive or sealant medium mayrequire extended cure at ambient temperature or other appropriate cureconditions, and it may be advantageous to conduct such cure with thelaminate structure in a fixture or other assembly in which thecompressive bonding is effectively completed.

In a specific aspect of the invention, each of the foraminous permeatesheets may constitute a foraminous material of from about 80 to about300 mesh size. Each of the foraminous permeate sheets may for examplecomprise a woven polymeric mesh, e.g., of a material selected from thegroup consisting of polyester, polypropylene, nylon, fluorocarbonpolymers such as polytetrafluoroethylene, polyethylene, and polysulfone,and composites comprising one or more of such materials.

The filter sheets used in the filtration cassette of the presentinvention may be of any suitable materials, such as a material selectedfrom the group consisting of cellulose, polyphenylene oxide,polysulfone, cellulose nitrate, cellulose acetate, regeneratedcellulose, polyether amide, polyphenylene oxide/polysulfone blends,mixed esters of cellulose, and polyether sulfone.

Furthermore, it is possible to optimize the separate processes withcross-flow filtration modules of variable channel velocities but ofuniform channel heights, given the fact that most commercial cross-flowmodules are only available in a single channel height. When the channelheight of a cross-flow filtration module is known, shear is directlyproportional to channel velocity of such module for the same solutionpassing by.

In the use of cross-flow filtration modules of the type described in theaforementioned patents, the specificity and speed of a desiredseparation is effected by a) fluid distribution in the cross-flowmodule, b) channel height of the cross flow module, c) channel length,d) shear rate, e) membrane pore structure, f) membrane structure, g)membrane chemistry, h) trans-membrane pressure, and i) pressure drop,which is a function of channel length, velocity and solution viscosity.

The approaches by others involving various additives and manipulationsof transmembrane pressure appear to be predicated on overcoming problemscreated by poor distribution of flow within the cross-flow module. It isnot to say that the addition of salts and solvents do not have a placein separation but without proper flow distribution the membraneseparation cannot be optimally operated nor will cleaning techniques befully beneficial. It will be appreciated, based on the disclosure hereinthat numerous heretofore expensive or difficult separations are renderedfar simpler and more economical by employing the techniques describedherein.

Thus, the invention relates in another aspect to optimizing the membraneseparation process, comprising:

-   -   selecting a cross-flow membrane module wherein the distance from        the inlet port to the outlet port is equidistant from the inlet        to outlet for each sub-channel of the device, i.e., each        sub-channel is of a same dimensional character;    -   selecting an optimal channel height;    -   selecting an optimal shear rate and/or channel velocity;    -   selecting an optimal transmembrane pressure;    -   selecting an optimal membrane pore size;    -   selecting an optimal temperature;    -   selecting an optimal channel length; and    -   selecting an optimal pressure drop which is the composite of the        optimal channel height;    -   the optimal shear rate and/or channel velocity;    -   optimal channel length; and    -   the viscosity of the solution being filtered.

Selecting a channel height can be performed mathematically orempirically by trial and error. In most animal manure applications,trial and error has been more appropriate due to the fact that theviscosity of the prefitered manure, manure digestate, or productsolution is rarely known, the nutrient levels and contiuent componentsare highly variable based on season, diet, and living conditions. Theobjective of channel selection is to minimize channel height with threecritical stipulations: first, the channel must be sufficiently high toallow the unrestricted passage of any larger material such as manuresolids; second, the channel should not cause excessive pressure drop andloss of linear efficiency; and third, the channel should be sufficientlyhigh as to allow the proper angle of attack for substances to encounterthe membrane pore and pass through the pore. The optimal channel heightis dependent on the length and viscosity of the solution.

Another aspect of the present invention relates to a stacked cassettecross-flow filter comprising cassette articles of the type describedabove.

Still another aspect of the present invention relates to a pair of endplates or manifold assembly in which the cassettes are secured foroperation as shown in FIG. 2.

Referring to FIG. 3, a vessel 14 is shown in which manure slurry isincluded into a cross-flow filtration cassette 18 to be separated into aliquid fertilizer in the permeate stream and a viscous concentratedfertilizer in the retentate stream. The components of the cross-flowfiltration cassette 18 are described in FIG. 1 and the separation isfacilitated by the use of a filtration cassette comprising amultilaminate array of sheet members of generally rectangular andgenerally planar shape with main top and bottom surfaces, wherein thesheet members include:

-   -   a first compressible retentate sheet of suitable material, e.g.        polysulfone, polyethersulfone, polycarbonate, urethane,        silicone, or other compressible material of construction,        having (i) at least one longitudinally extending rib or        partition element 6, such partition element(s) when provided in        multiple configuration being transversely spaced apart from one        another and being of substantially the same height and        substantially parallel to one another to define a single or a        series of channels 8 between the partitions, extending        longitudinally between the respective inlet 10 and outlet 12        basin openings of associated filter elements and permeate sheet        members, on both faces thereof, (ii) permeate passage openings        13 at side portions of the sheets, and (iii) the retentate sheet        aligned to the first sheet of filter material at respective end        and side portions thereof, with the basin openings and permeate        passage openings of the associated sheet members in register        with one another and the permeate passage opening of the        retentate sheet member being circumscribingly compressed to the        first sheet of filter material, and with a central portion of        the first sheet of filter material and the retentate sheet        member being unbonded to permit permeate contacting the        retentate sheet member to flow through the first sheet member of        filter material to the foraminous permeate sheet member;    -   a first sheet member of filter material having (i) multiple        basin openings, of a suitable shape, e.g., polygonal,        semicircular, or sector shape, at each of opposite end portions        of the sheet member defining respective inlet 10 and outlet 12        passages, each basin being bounded by generally linear side        edges defining corners of the basin at respective intersections        of the side edges, and (ii) permeate passage openings 13 at the        side portions of the sheet member, wherein the first sheet        member of filter material is bonded to the foraminous permeate        sheet member at their respective end and side portions, with        their basin openings and permeate passage openings in register        with one another and the basin openings being circumscribingly        bonded at respective end portions of the first sheet member of        filter material and the foraminous permeate sheet member, and        with a central portion of the first sheet member of filter        material and the foraminous permeate sheet member being unbonded        so as to define a central portion permeate channel of the        foraminous permeate sheet communicating with the permeate        passages in the first sheet member of filter material and in the        foraminous permeate sheet member;    -   a forminous permeate sheet member of screen or mesh material,        having (i) multiple basin openings of suitable shape at each of        opposite end portions of the sheet member defining respective        inlet 10 and outlet 12 passages, each basin being bounded by        generally linear side edges defining corners of the basin at        respective intersections of the side edges, and (ii) permeate        passage openings 13 at the side portions of the sheet member;    -   a second sheet member of filter material having (i) multiple        basin openings at each of opposite end portions of the sheet        member defining respective inlet 10 and outlet 12 passages, each        basin being bounded by generally linear side edges defining        corners of the basin at respective intersections of the side        edges, and (ii) permeate passage openings 13 at the side        portions of the sheet member, wherein the second sheet member of        filter material is compression sealed to the retentate sheet        member at their respective end and side portions, with their        basin openings and permeate passage openings in register with        one another and the permeate passage opening of the retentate        sheet member being compression sealed to the second sheet member        of filter material, and with a central portion of the second        sheet member of filter material and the retentate sheet member        being unbonded to permit permeate contacting the retentate sheet        member to flow through the second sheet member of filter        material; and    -   a second compressible retentate sheet member of suitable        material, e.g. polysulfone, polyethersulfone, polycarbonate,        urethane, silicone, having (i) at least one longitudinally        extending rib or partition element 6, provided that when        multiple partition elements are employed, the partition elements        are transversely spaced-apart from one another, such partition        elements being of substantially the same height and        substantially parallel to one another, to define a single        channel 8 or a series of channels between the partitions,        extending longitudinally between the respective inlet and outlet        basin openings of the filter elements and permeate sheet        members, on both faces thereof, (ii) permeate passage openings        13 at the side portions of the sheet member, and (iii) the        retentate sheet compression sealed to the second sheet of filter        material at respective end and side portions thereof, with their        basin openings and permeate passage openings in register with        one another and the permeate passage opening of the retentate        sheet member being compression sealed to the second sheet member        of filter material, and with a central portion of the first        sheet member of filter material and the retentate sheet member        being unbonded to permit permeate contacting the retentate sheet        member to flow through the second sheet member of filter        material to the foraminous permeate sheet member.

Notably, nutrients can be removed from both the permeate stream andretentate stream including ammonia, phosphorus, potassium and othertrace elements that can be used as fertilizer additives or furtherpurified and added to animal feed.

As shown in FIG. 3, the manure slurry or digestate is contained invessel 14 and moved into the cross-flow filtration unit of the presentinvention 18, wherein the permeate steam is separated and introducedinto the liquid fertilizer vessel 20 and can be used for liquidfertilizer. Optionally the liquid fertilizer can be further treated bypassing through a second cross-flow filtration unit of the presentinvention for concentration of desired target products such as nitrogenand/or phosphorus and producing usable water in the permeate. Optionallythe retentate can be redirected back to the liquid fertilizer tank.Furthermore the viscous retentate fertilizer may be optionally processedthrough drying setup as shown in FIG. 8 to produce a flake or powdersolid fertilizer.

FIG. 4 illustrates the consistency of the manure slurry or digestateintroduced into the vessel 14 of FIG. 3 (left side of the photo) and theincreased viscosity of the concentrate retained in the viscous retentatestream (right side of the photo) that can be further processed by dryingto provide a solid fertilizer. Generally, the manure digestate comprisesfrom about 3 to 8% solids and with the use of the presently disclosedcross-flow filtration cassette there is available about an 80 to 90%volume reduction (5 to 10× concentration). As such, the viscousretentate, after treatment, can include from about 15% solids (5×) toabout 80% (10×) solid in the paste.

FIGS. 5, 6, and 7 provide graphs showing the amount of specific elementsseparated from the manure, that being, the amount that is retained inthe retentate concentration and that which has moved into the permeateusing the cross-flow filtration cassette of the present invention. Thefigures show three columns wherein the first column (left side) includesthe starting digestate or manure, the middle column includes the amountof a specific element in the permeate stream and the end column (leftside) shows the amount of a specific element in the concentratedretentate stream.

FIG. 5 shows the difference in amounts of specific element of both amanure digestate and screen raw manure. Notably, the digestate providedincreased amounts of the elements in the permeate streams, such as,phosphorus, magnesium, calcium and potassium. The concentrate in bothtested manure types included essentially the same amount of phosphoruswhich was clearly increased relative to that in the permeate stream.

FIG. 6 shows the filtration difference when using two different filterscreens in the cross-flow filtration cassette. Filter 1 is a highlyhydrophilic 10 kD ultrafiltration membrane and Filter 2 is a polymerictype 10 kD ultrafiltration membrane. Reviewing the results, Filter 2provides for increase amounts of phosphorus, calcium and magnesium inthe permeate relative to Filter 1. In contrast, Filter 1 provides for agreater concentration in the concentrate (retentate) of phosphorus,calcium and magnesium. As such, depending on the desired product, thesystem, membrane size and type can be optimized to selectively isolatethe desired product in specific separation cuts. Preferably the filterhas a NMWL in the range of 5 kD to 30 kD.

FIG. 7 shows NH₃/NH₄ passes freely through the membrane. Thereforemanure can be fractionated into P rich fractions (concentrate) andNH₃/NH₄ rich fractions (permeate) for differential application tofields.

FIG. 8 shows a preferred embodiment of a drying unit used in theprocessing of a viscous stream of manure. In a preferred embodiment, theviscous manure from the cross flow filtration system 24 is introducedinto an optional mixing system 26 to ensure continuity of the materialas it is cast, extruded, or wiped as a thin expanded and uniform layer30 onto a moving conveyor belt 28. The conveyor belt may be constructedof any material such as polymeric, rubber or metal and can optionally beheated. Preferably the uniform thin layer is about 0.05 to about 0.01inch in thickness and preferably when dried is reduced to about 0.001 to0.005 inches. The chamber 32 provides air flow to evacuate the moistureand may optionally provide a heated belt, and/or a heating system fordrying of the thin layer of the manure. In this system additionalheating chambers may be added to ensure drying of the material. When thematerial is sufficiently dried it is moved into a container 34 forfurther transport to an end user.

Notably the drying unit described in FIG. 8 may also be applicable inproducing high solids concentrations in the drying of components, suchas starch, dairy proteins, algae, proteins, waste water solids, zeolite,and others. With a uniform thin film it may be possible to dry materialsmore consistently and without denaturing sensitive material such asprotein-containing materials. When materials are inconsistent inconcentration, size and shape the actual energy seen by the materialmust therefore also be inconsistent. Materials with maximum exposedsurface area dry first but become overexposed to additional energy whilethe more dense materials are still drying. Thus proteins may bedenatured while larger particles are still in the process of drying.Thus the drying system of FIG. 8 provides for less heat input, lowerenergy cost, less denaturing of sensitive protein containing material,and decreased drying time. Further, attaching the drying system directlyto the filtration system of the present invention provides for anintegrated system that eliminates the high cost of specific equipmentsuch as drum dryers or filter presses. Still further, the integratedsystem does not require the use of additives such as diatomaceous earth,polymers.

That which is claimed is:
 1. A process for treating a manure slurry inorder to produce (a) fertilizer products having optimized concentrationsof at least one of calcium and magnesium, and (b) potable or non-potablewater, the process consisting of: separating the manure slurry into afirst permeate stream and a viscous first retentate stream by passingthe manure slurry through a first cross-flow filtration cassette,wherein the first permeate stream is directed to a liquid fertilizervessel and the viscous first retentate stream is a concentratedfertilizer, moving the liquid medium in the liquid fertilizer vessel toa second cross-flow filtration cassette to separate a second permeatestream from a viscous second retentate stream, wherein the secondpermeate stream comprises potable or non-potable water, and redirectingthe viscous second retentate stream to the liquid fertilizer vessel toconcentrate nutrients present in the manure slurry, wherein eachcross-flow filtration cassette comprises: a pair of end plates; and atleast one array of sheet members of generally rectangular and generallyplanar shape with main top and bottom surfaces, wherein the at least onearray of sheet members is secured between the pair of end plates,wherein the sheet members include in sequence in said array a firstretentate sheet, a first filter sheet, a permeate sheet, a second filtersheet, and a second retentate sheet, wherein each of the sheet membersin said array has at least one inlet basin opening at one end thereofand at least one outlet basin opening at an opposite end thereof,wherein each of the sheet members in the array has at least one permeatepassage opening at longitudinal side margin portions of the sheetmembers, wherein each of the first and second retentate sheets have amultiplicity of channel openings extending longitudinally between theinlet and outlet basin openings, and said retentate sheets are bonded toan adjacent filter sheet about peripheral end and side portions thereof,wherein the inlet basin openings, outlet basin openings, and permeatepassage openings are in register with one another and the permeatepassage openings of each of the retentate sheets are circumscribinglybonded to the adjacent filter sheet, with a central portion of each ofthe retentate sheets and adjacent filter sheets being unbonded to permitpermeate contacting the retentate sheet to flow through the filter sheetto the permeate sheet to form a permeate stream.
 2. The method of claim1, wherein each cross-flow filtration cassette can be optimized toselectively isolate at least one of calcium and magnesium in the viscousfirst retentate stream relative to the viscous second retentate stream.3. The method of claim 1, wherein the manure slurry comprises urine andfecal matter from dairy cattle, beef cattle, swine, sheep, goats,poultry, horses, rabbits or other confined animals.
 4. The method ofclaim 3, wherein the manure slurry further comprises wasted feed,bedding, spilled water, flush water, or wash water.
 5. The method ofclaim 1, wherein the manure slurry is about 80% to about 95% liquid byweight.
 6. The method of claim 1, wherein the manure slurry is providedfrom a waste manure lagoon.
 7. The method according to claim 1, whereina concentration of phosphorus in the permeate streams relative to theconcentration of phosphorus in the retentate streams can be optimized bychanging a material of the first and second filter sheets.
 8. The methodof claim 1, wherein the manure slurry is flowed over the first andsecond filter sheets in the first cross-flow filtration cassette at ashear force that opposes accumulation of solids on the surface of thefirst and second filter sheets, thereby forming the viscous firstretentate stream.